1. Field of the Invention
The present invention relates to a distributed processing type control system and, more particularly to a distributed processing type control system which is capable of executing a programmable control by writing control data in a rewritable non-volatile memory such as an EEPROM.
2. Description of Related Art
There is known a fully distributed processing type control system which has a plurality of sub-controllers for controlling individually a plurality of local devices different from each other.
Japanese Laid-open Patent Publication No. 6-219187 discloses a master-slave distributed processing type control system. In this apparatus, a plurality of sub-controllers which share partial controls different from each other are connected through respective exclusive lines to a master controller which executes supervising control for the sub-controllers. The master controller stores therein vehicle control characteristics parameters corresponding to a plurality of drivers, and selects and commands to the sub-controller one of the vehicle control characteristics parameters in correspondence with a specified one of the drivers.
In this fully distributed processing type control system, when an external tool such as a diagnosing device or a teaching device collects data from each sub-controller or issues a command to each sub-controller, it is required to execute each time a communication between the external tool and each sub-controller through a serial bus, for instance.
More specifically, in this fully distributed processing type control system, each sub-controller is required to have its own operational function of communication with the external tool. In the case that the sub-controller is designed to execute a control variably, each sub-controller is required to have its own non-volatile memory for the variable control. Thus, the size of the entire control system will expand remarkably as the number of sub-controllers increases.
In the above master-slave distributed processing type control system, the external tool is required only to execute the communication with the master controller, because the master controller manages distribution of control programs of the sub-controllers and collects diagnosis data in a centralized supervising manner. In this system, however, it is likely that the master controller will be required to have an increased control size and an increased communication processing, because the master controller supervises all the sub-controllers individually. Further, it is also likely that the failure in the master controller will lessen the entire operational function of the system. Still further, in a vehicle control system, it may be required that each sub-controller has its own specification or is different depending on the type of vehicle. Thus, the specification of the master controller must be changed accordingly.